Electron-discharge device



Sept. 4, 1928. 1,683,202

W. A. M DONALD ELECTRCN DISCHARGE DEVICE Filed April 9, 1926 INVENTOR MW/mz fl. Maria/mid Y M4,?W, M7 M,

ATTORNEY Patented Sept. 4, 1928.

. UNITED STATES 'WTLLIAI A. MACDONALD, OF LITTLE NECK, NEW YORK, ASSIGNOR TO HAZELTINE 00B- PATENT OFFICE.

PORATION, 0F JERSEY CITY, NEW JERSEY, A CORPORATION OF DELAWARE.

ELEOTRON-ZOISCHABiGE DEVICE.

Application filed April 9,

This invention relates to electron discharge devices, or vacuum tubes.

In amplifiers and radio receivers, especially those in which radio-frequency currents are amplified, it is known that the in herent capacity between the grid and plate electrodes of the amplifying tubes causes undesirable couplings between the various circuits which tend to produce undesirable oscillations. Various circuit arrangements have been devised to neutralize the effect of this inherent coupling capacity, and in all these arrangements the circuits are designed to neutrahze a predetermined inherent capacity. It has been found in practice, however, that there is lack of uniformity of this inherent capacity even among vacuum tubes of the same t pe so that it is difficult to effect the desired neutralization,

In accordance with the present invention, it is proposed to add a separate adjustable condenser which will supplement and increase the effective valve of the inherent inter-electrode capacity which it is desired to neutralize. The electrostatic capacity of this condenser is adjustable so that all the tubes of a t e may be made exactly alike even though t ere may be variations in the natural capacity between certain of the electrodes. Furthermore with a given neutralizing capacity, the degree of neutralization may effectively be varied by adjustment of this supplemental condenser.

In the drawings:

Fig. 1 represents a vertical cross-section of a vacuum tube in which the present invention is incorporated.

Fig. 2 shows a perspective view of the base of a vacuum tube of Fig. 1 in which the terminal contacts extends through the bottom.

Fig. 3 shows a side elevation of a portion of a vacuum tube in which the terminal contacts project through the side of the base, and in which two adjustable supplemental condensers are provided.

Fig. 4 shows a section taken on the line 4-4 of Fig. 3 showing in detail the adjustable contacts by which the capacities of two supplemental condensers may be varied.

Flg. 5 is a circuit arrangement of one form of radio receiver in which vacuum tubes provided with the present invention may be em loyed.

rel-m especially to Fig. 1, there is 1926. Serial No. 100,826.

shown an evacuated envelope 1 in the press of which is mounted a plate 13. and a grid 14 consisting of a fine wire wound spirally upon two wire supports. Within the grid and plate there is located a filament 26 suitably suported by wires mounted in the press. A. base, generally designated 2, including a collar 3 is cemented to the envelope 1 by means of insulating material 4 through which the lead-in wires of the various electrodes extend; The late 13 is electrlcally connected by a lea -in wire 18 to a threaded sleeve 8 secured in an opening at 7 1n the collar 3 of the base. Wire 17, soldered to this sleeve, is connected to the plate terminal contact 5 extending through the insulating material 24, This material supports the various terminal contacts of the tube and closes the end of the collar 3 to which it is secured. The lead-in wire 15, connected to the grid, 1s soldered to a lug 9 staked in an opening in the collar 3. This lug terminates in a condenser plate or armature 10 for a purpose to be described, and is also electrically connected by the wire 16 to the grid contact gextending through the insulating material A threaded member 11 terminating in a condenser plate or armature 12 is threaded in the sleeve 8 and has its free end provided with a kerf to receive a screw driver passed through the opening at 7 by which it is adustab e to vary the spacing and hence the electrostatic capacity between the armatures 10 and 12. It will be noted that the capacity between these armatures supplements the inherent capacity existing between thegrid 14 and the plate 13. If desired, the opening at 7 may be filled with sealing wax or other suitable substance 7 after the capacity is adjusted, so that the adjustment cannot be easily tampered with.

In Fig. 3 there is shown a modified form of the invention wherein the contacts of the tube 19, 20 and '21 extend throughthe side of the base for use with a vacuum tube socket such as is disclosed in m co pending application Serial No. 31,736, ed May 21, 1925. As shown in Fig. 4, the armature 10 is connected to the grid contact 20 while the adjustable armature 12 is threaded in the plate contact 19. In certain circuit arran ements, it is desirable to have tubes in which the inherent capacity between the filament and grid or plate, is uniform. For this reason, an armature 27, adjustable with respect to armature 10 and electrically connected to filament contact 21, is provided, whereby an adjutable supplemental capacity is provided between the plate and filament. It will thus be understood that by means of the present invention the inherent capacity between grid and plate, the inherent capacity between filament and grid, and the inherent capacity between plate and filament can be individually adjusted to any desired standards. It will also be understood that a similar arrangement wherein the grid-filament capacity or the plate-filament capacity, is adjustable, may be included in the type of tube base shown in Fig. 1, although because of the fact that Fig. 1 1s a sectional view, the filament terminals are not indicated in the drawing. They are, however, shown unmarked in Fifie2.

ferring to Fig. 5 there is diagrammatically indicated the circuit arrangement of a radio receiver having one stage of radiofrequency amplification and a detector D. The dot-and-dash line between the primary and secondary coils of the coupling transformer 30, together with the suggested break in the connection between neutralizing condenser 29 and the mentioned secondary coil, is intended to indicate that additional hi hfrequency amplifying stages similar to t at shown may precede the detector. As was reviously stated, there is represented an inherent capacity 25 existing between the plate electrode 13 and the grid 14, of tube 28. In order to neutralize the effect of this inherent capacity the circuits are arranged to include a neutralizing capacity 29 in accordance with the arrangement disclosed in the Patent No. 1,533,858 to Louis A. Hazeltine. The vacuum tube 28, between whose grid electrode 14 and plate electrode 13 there exists inherent capacity 25, is provided with means introducing a supplemental capacity according to the present invention including the armature 10 and the adjustable armature 12 efl'ectively connected in parallel with the inherent ca acity between the mentioned electrodes 0 the tube.

It will be readily recognized that by the present invention the inherent capacities of various tubes may be rendered exactly uniform, whereby the tubes may be interchangeable for use in neutralized radio-frequency amplifying stages, or in other circuits which require precise values of inter-electrode capacities. For manufacturing or other reasons, it is sometimes desirable to utilize a reasonably large neutralizing capacity. In such event the use of a supplemental gridplate capacity, according to this invention, makes possible the employment of a neutralizing capacit of any desired size while allowing also or any desired turns ratio between the plate-circuit coil and the neutralizing coil, as required by the neutralization equation given in the mentioned Hazeltine patent. The degree of neutralization may then effectively be adjusted by variation of either the neutralizing capacity or the supplemental capacity, or by variation of both.

I claim:

1. In an electron discharge device including more than two electrodes enclosed in an evacuated envelope, a plurality of means outside said envelope mechanically attached to said device and directl connected to two of said electrodes for a justing the effective electrostatic capacity between said two electrodes within capacity values of an order of magnitude commensurate with the value of capacity naturally inherent between said electrodes, at least one of said means being manually adjustable for varying said effective electrostatic capacity.

2. A vacuum tube structure comprising a base and an evacuated envelope enclosing a plurality of electrodes and manually adjustable means secured to said base and directly connected to two of said electrodes for adjusting the effective electrostatic capacity between the said two electrodes.

,3. A vacuum tube structure comprising a base and evacuated envelope enclosing a plurality of electrodes, and a manually adjustable condenser secured at the base of said structure and directly connectedto two of said electrodes for supplementing the effective electrostatic capacity naturally inherent between said two electrodes.

4. A three-electrode vacuum tube structure comprising an evacuated envelope enclosing a grid electrode, a plate electrode and a filament electrode, said electrodes being supported on a press, and an adjustable condenser secured at the base of said structure and electrically connected to said grid and plate electrodes for supplementing the eilective electrostatic capacity naturally inherent between said grid and plate electrodes.

5. A vacuum tube structure comprising an envelope enclosin a plurality of electrodes, a base through w ich contacts protrude for making outside connections to said electrodes, and a condenser secured at the base and adjacent said contacts and having two armatures mechanically distinct from said electrodes but electrically connected to two of them, said condenser being outside said envelope, one of said armatures being adjustable with respect to the other whereby the total efi'ective electrostatic capacity between said two electrodes may be adjusted.

6. A vacuum tube structure comprising an evacuated envelope enclosing grid, plate and filament electrodes, a base through which contacts protrude for makin outside connections to said electrodes, an a conchanicall tain total effective denser secured at the base and adjacent said contacts and having two armatures medistinct from said electrodes but electrical y connected, respectively, to said grid and late electrodes, said condenser belng outsi e said evacuated envelope, one of said armatures being adjustable relative to the other-whereby the total effective electrostatic capacity between said grid and plate electrodes may be adjusted.

7. For a vacuum tube amplifying system wherein a neutralizing condenser of a certain capacity is included to neutralize a cerrid-plate coupling capacity of an ampli ying tube of said systerm, a vacuum tube structure adapted to be substituted for said amplifying tube having a value of grid-plate capacit different from that of said amplifying tu e and an adjustable condenser mechanically secured to said tube structure, armatures of said condenser being electrically connected, respectively, to the grid and plate electrodes of said tube structure, and means for adjusting the capacit of said condenser whereby the total effectivegrid-plate coupling capacity of said tube structure may be equal to that of said amplifying tube and said neutralizing capacity may be eiiective to neutralize the total effective gridlatecoupling capacity of said vacuum tu e structure.

In testimony whereof I aflix my signature.

WILLIAM A. MACDONALD.

denser secured at the base and adjacent said contacts and having two armatures mechanicall distinct from said electrodes but electrical y connected, respectively, to said id and (flute electrodes, said condenser bemg outsi e said evacuated envelope, one of said armatures being adjustable relative to the other whereby the total efi'ective electrostatic capacity between said grid and plate electrodes may be adjusted.

7. For a vacuum tube am lifying system wherein a neutralizing con enser of a certain capacity is included to neutralize a certain total efl'ective rid-plate coupling capacity of an am li g tube of said .system, a vacuum tu e structure ada ted to be substituted for said amplifying tu e having a value of grid-plate capacit difierent from that of sad amplifyin tu e and an adjustable condenser mec anically secured to said tube structure, armatures of said condenser bein electrically connected, respectively, to 0 grid and plate electrodes of said tube structure and means for adjusting the capacit of sald condenser whereby the total efi'ectlve' grid-plate coupling capacity of said tube structure may be equal to that of said amplifying tube and said neutralizing capacity may be eii'ective to neutralize the total efi'ective gridlatecoupling capacity of said vacuum tu e structure.

In testimony whereof I aflix my signature.

WILLIAM A. MAODONALD.

CERTlFICATE 0F CORRECTION.

Patent No. l, 683. 202.

Granted September 4, 1928, to

WILLIAM A. MacDONALD.

It is hereby above numbered patent requiring correction as follows:

certified that error appears in the printed specification of the Page 1, line 23, for the word "valve" read "value", and line 40. for "extends" read "extend"; and that the said Letters Patent should be read with these corrections therein that the same may conform tothe record of the case in the Patent Office.

Signed and sealed this 23rd day of October, A. D. 1928.

(Seal) M. J. Moore, Acting Commissioner of Patents. 

